feat: add lint to detect RLS policies that allow access to anonymous users

[kangmingtay]

What kind of change does this PR introduce?

• adds a lint to check if there are any policies that allow access to anonymous users

What is the current behavior?

• currently, if a user enables anonymous sign-ins for their project, they need to manually check existing RLS policies to see if any of them are compromised.

What is the new behavior?

• this lint will highlight any policies that:
  • are associated to the authenticated, public, or any other role members
  • policies that don't contain the auth.jwt()->>'is_anonymous' expression in the policy definition

Additional context

Add any other context or screenshots.

[kangmingtay]

blocked on deciding how we can run lints conditionally on the platform - currently, there's no way to conditionally execute a lint from the splinter.sql file